Software Defined Networking – CompTIA A+ 220-1101 – 2.2

We have extended the functionality of physical networking devices into cloud-based infrastructures. In this video, you’ll learn about the structure and usability of software defined networking.

The advent of cloud computing has changed networking in many ways. And if you’re a network administrator, you know that in the cloud, we don’t usually have physical routers, switches, and other infrastructure devices. Instead we need to take these networking platforms we use in the real world and move them into the virtualized cloud based world.

One way that we’re able to do this is through the advent of Software Defined Networking or SDN. With software defined networking, we take those devices like switches, routers, firewalls and other networking infrastructure devices and we change them to be a software based platform that we could use in the cloud. This means that we might take something like a switch and separate all of the functions of the switch into individual pieces. We can then take these pieces and then create software versions that we can then run in the cloud.

There are commonly three layers or three ways to separate these devices so that we can create some consistency across all of these networking components. The first layer would be the infrastructure layer. Sometimes we hear this referred to as the data plane of that device. So it’s common that this data plane would do the forwarding, the trunking, the encrypting, the network address translation, or anything else that needs to occur at that packet level.

When our routers and switches need to forward this traffic in the data plane, they need some type of reference to know where this traffic will be going. Most of those references will be in the control layer or control plane of that device. So if you have dynamic routing protocols, a forwarding table in a switch, a network address translation table in a router, all of those are contained in the control plane. And of course, you or some other process is in charge of managing that device.

To be able to manage it, we need to log in or access the device via an API or Application Programming Interface. And all of that access is provided at the application layer or management plane of that device. So when you SSH into a router, when you bring up a graphical front end of a firewall, you’re managing that device from the management plane.

Let’s see how this software defined networking would apply to a physical device. And in this case, this physical device appears to be a switch, but this could be a router or firewall or any other infrastructure device. Let’s start first with that infrastructure layer or the data plane. If you’re connecting to a switch or you need traffic forwarded between different interfaces on a switch, that all occurs in that data plane. This means we’ll take anything that may be forwarding this traffic on that device and create a software version of that that we call the data plane.

These devices also need the tables and forwarding structure to be able to understand where traffic is coming from and where you’ll be forwarding it to, and all that occurs in the control layer or the control plane. And lastly, you’ll be managing this device probably through a console port or management interface to the device, and that section of the device can be created as the management plane. Obviously with software defined networking, there is no physical device, but you can see where the data plane, control plane, and management plane are pulled from our physical devices to create this software based networking infrastructure.

This now creates modular layers that you can extend between devices or create new devices all based on the software defined networking. If we start, for instance, at the bottom, we know that network traffic will be traversing different devices all at the data plane. So communication between those can occur solely between those particular layers. A device may need to send or receive dynamic routing protocols or create tables for forwarding, and all of those can be done at the control layer or the control plane of software defined networking.

And the layer that you’re going to manage these devices from will be the management plane. We usually access the management plane through secure shell, simple network management protocol, or an application programming interface. You can see that the software defined networking takes these very standard categorizations and extends them across multiple networking devices to create a very modular architecture. This allows you to have a software based version of these network devices that we use on our physical networks and be able to deploy them and use them in a cloud based infrastructure.